The present invention relates to a device for breaking the nicks connecting two edges of a line of cut of stacked sheets of cardboard placed on horizontal support and transportation means for moving the said sheets in a longitudinal direction, comprising upper claiming means for claiming the stacked sheets against the said support means, first means for longitudinally moving apart the said support and transportation means and the said clamping means on both sides of a transverse line of cut of the said stacked sheets, and second means for moving apart transversely the said support and clamping means on both sides of a longitudinal line of cut.
The devices of this type are used in particular during manufacture of cardboard boxes obtained by folding pre-cut and grooved cardboard blanks formed from sheets of cardboard.
Such devices for separating stacks of pre-cut sheets by clamping the stacks of sheets on both sides of the pre-cutting line and exerting traction to break the the nicks connecting these sheets exist. One of the them is described, for example in FR 2xe2x80x2372xe2x80x2025. However, this device is limited to the cutting of stacks of sheets on both sides of a transverse line. However, in most cases, in particular during manufacture of small packages a plurality of cardboard blanks are disposed side by side in the direction of both the length and the width of the cardboard sheet so that it is necessary to be able to separate the stacked sheets of cardboard not only in the transverse direction but also in the longitudinal direction of these sheets.
In CH 646xe2x80x2665 a device has already been proposed which permits separations to be carried out in two directions perpendicular to each other in the direction of the length of the cardboard sheets and in the transverse direction without needing to turn the sheets by 90xc2x0 after a first cutting procedure. To this end this device has four support tables aligned two by two transversely and longitudinally with respect to the direction of movement of the stacks of cardboard sheets. These four tables are associated with four pressing members and can be moved apart from each other both longitudinally and transversely in order to effect separations between the stacks of sheets.
This device has certain drawbacks and limitations. These drawbacks include the fact that the separation along two lines perpendicular to each other is carried out by moving the tables and pressing members in a direction forming an angle of 45xc2x0 with respect to the two lines of separation The force required is greater than it would be if it were directed perpendicular to each of the lines of separation. Consequently the stacks must be clamped more strongly and this poses a risk of marking the cardboard sheets which are at the extremities of the stacks.
The limitations of the device result from the fact that it does not permit a separation to be carried out transversely to the direction of movement of the sheets of cardboard. However, it is frequently the case that it is necessary to effect a greater number of separations especially when small packages, for cigarette packets or boxes for bottles of perfume for example, are being produced.
The aim of the present invention is to overcome at least partially the drawbacks of the above-mentioned solutions.
To this end the object of this invention is a device for breaking the the nicks connecting two edges of a line of cut of stacked sheets of cardboard placed on horizontal support and transportation means for moving the said sheets in a longitudinal direction.
The main advantage of this invention resides in the fact that it permits production of an unlimited number of cardboard blanks in the direction transverse to the main or longitudinal direction of movement of the stacks of sheets.
The transverse transportation means for the stacked sheets are preferably flexible elements, of which the two ends are attached to the supports of the longitudinal conveyor and pass over the transverse supports after having been passed around two sheaves fixed to the ends of these transverse supports.
For this reason, when the supports of the longitudinal conveyor are moved laterally in one direction, the part of the flexible element passing over the transverse supports moves in the opposite direction. By reason of these movements in opposite directions the length of the transverse movement of the supports of the longitudinal conveyor is added to that of the movement of the stacked sheets so that the relative displacement for bringing the lines of separation of the stacked sheets between the two supports of the longitudinal conveyor in order to separate them is twice as great as the actual displacement of each one of them. This permits a reduction in the width of the device for breaking the the nicks between the stacked sheets with respect to a system in which the support of the longitudinal conveyor would be fixed in the lateral direction, or a system in which the stacked sheets would be fixed in the lateral direction.
Other features and advantages of the device which is the object of the present invention will become clear during the following description which will be given with the aid of the attached drawings which illustrate schematically and by way of example an embodiment of the device for breaking the nicks connecting two edges of a line of cut of stacked sheets of cardboard.